Multifamily Housing Characteristics and Tenant Satisfaction

This paper examines the long-term impact of structural features and physical amenities on the residential satisfaction of renters in multifamily housing. A cumulative logit analysis of 7,206 rented multifamily units in the 2005 American Housing Survey indicates that features creating separated space (additional room, bathroom, garage/carport, or balcony/patio) were associated with significantly higher satisfaction, even when holding total unit area constant. Conversely, violation of space separation by noise intrusion through walls, floors, or ceilings created dramatically negative effects. Other amenities such as a fireplace, disposal, or dishwasher had no statistically significant impact. Tracking a cohort of 5,170 rented multifamily units from 1997 to 2005 revealed somewhat similar effects on the satisfaction trajectory of residents during this period. More bathrooms, bedrooms, and other rooms, as well as the presence of a balcony/patio were associated with satisfaction improvements. Analyzing cohort units undergoing modifications during the tracking period revealed that the addition of a bathroom or central air conditioning had the clearest impact on satisfaction, followed by the addition of a balcony/patio, other room, dishwasher, or garage/carport.     

Case Study-Based Challenges of Quality Concrete Finishing for Architecturally Complex Structures

This paper focuses on the procedure utilized in the construction of tilt-up irregular concrete panels that are constructed on-site using concrete slabs and wooden formwork. The case study required high-quality concrete finishing. The erection and installation procedure called for a maximum panel-to-panel joint tolerance of 1.27?cm (0.5?in.), often 90° joints between panels. To meet precision requirements, the casting slabs were leveled and flattened with laser screed technology and smoothed with chemical solutions. To ensure that the final result met expectations, a mock-up model was built using different types of materials and to simulate site constraints. The architectural design is a composition of precast concrete panels like “Lego” pieces assembled similarly to a jigsaw puzzle. The unique construction process required a state-of-the-art analysis to produce the set quality. Quality conditions as set by the owner included creating a smooth concrete surface on all panels while avoiding damages and reducing equipment and material costs. The proposed methodology is described through its implementation on the case study, which is also described in this paper.     

建筑物公共区域能量有效性确定

公共建筑中公共区域人流量变化很大,能量的需求也应随着人流量的变化而变化。但传统模式下能量输出却很少考虑人流量的变化,这就造成了部分能量无效。如何评价能量有效性,以减少能量浪费是建筑节能需要研究的问题。提出了能量利用效率概念,用于判断人对能量的利用程度,给出了能量利用效率的计算方法。在某医院公共候诊区进行了工程实验,对比实验前后的能耗状况发现,能量利用效率能够评估能量有效性的状况,以提高能量利用效率为控制目标,可以较大幅度提高建筑物公共区域能效。     

建筑物目标高分辨率SAR图像模拟方法

随着TerraSAR-X,Cosmo-SkyMed和Radarsat-2等高分辨率合成孔径雷达(SAR)卫星系统的升空,星载SAR图像空间分辨率达到了米级。在这些高空间分辨率SAR图像中,单个建筑物结构的散射特征能够得到明显的展现,推动了SAR在城市监测中的应用。而城市环境的复杂性给SAR图像的解译和应用带来了巨大的挑战,由于SAR图像模拟有助于图像的解译和应用,因此城市目标高分辨率SAR图像模拟成为一个研究热点。提出了一种基于射线追踪法的图像模拟方法,它能够模拟城市目标SAR图像上叠掩、阴影和多次散射等主要特征,非常有利于SAR图像的解译。该模拟方法首先构建虚拟SAR传感器,发射电磁波射线与场景中三维模型相互作用,并接收回波信号成像,电磁波的传播以及与场景的多次散射在整个过程中都能够被追踪。为了评价该模拟方法的有效性,首先通过模拟平顶屋、尖顶屋模型的SAR图像,然后选择国家体育馆和大场景小区三维模型作为输入,将生成的模拟图像与真实TerraSAR-X聚束模式图像进行比较。结果表明:该模拟器能够模拟城市目标的散射特征并应用于图像的理解和变化检测。     

Airtightness Testing of Two-?and Three-Unit Buildings with a Single Fan

This paper presents a method for the field measurement of airtightness for two-?and three-unit buildings using only one fan pressurization system, commonly referred to as a blower door. The main advantage of this single-fan method is its lower equipment and labor cost as compared with multiple-fan methods. Results from consecutive tests in the individual units are used to prepare a set of simultaneous equations for airflow, allowing for the calculation of the air leakage characteristics of both the interior partitions and the exterior envelope on a unit-per-unit basis. Tests were performed on four buildings using the single-fan method and were compared with those obtained with a two-fan method. Test results indicate that the single-fan method may be of value as an inexpensive method of estimating the airtightness of two-?and three-unit residential buildings.     

Pilot Study for the Performance of a New Demand Control Ventilation System in Hong Kong

There are different ventilation control methods for outdoor air quantity in air-conditioned spaces to reduce the energy consumed in cooling the outdoor air. Demand controlled ventilation (DCV) is an important strategy to control the outdoor air quantity. However, the current practice in DCV systems creates several problems for air-conditioned office buildings. Although metabolic carbon dioxide (CO2) concentration is mainly used as a surrogate indicator for ventilation adequacy, the conventional DCV system does not seriously consider the placement location of the CO2 sensor, and it does not take into account the adverse effects of the consequential increase in pollutant concentrations in the indoor space when the fresh airflow rate is reduced. In this study, a long period of subjective and objective measurements were conducted in an occupied office to examine its suitability for conversion to a new demand controlled ventilation system (nDCV). After the feasibility investigation, an nDCV system was developed to optimize the energy consumed for outdoor air ventilation while providing the desirable thermal comfort and indoor air quality. The true optimization of this nDCV is achieved by a new concept of the optimized indoor air quality window which determines the most representative locations for the indicator sensors. A minimum ventilation rate is determined by a calibration procedure for the pollutant inventory of a building, taking into account the infiltration characteristics. Radon gas, which is a notorious carcinogenic indoor pollutant, is used as a reference to determine the minimum fresh airflow rate. The findings show that this nDCV system reduced 16% of fresh air cooling energy consumption without jeopardizing the thermal comfort and indoor air quality.     

Stiffness-Damping Simultaneous Identification under Limited Observation

A more reliable and stable method, compared to the previous one developed by the present writers, of stiffness-damping simultaneous identification of shear-type building structures is proposed using stationary random records under limited observation. It is shown that when stationary random horizontal accelerations are recorded at the floors just above and below a specific story in a shear building model, the story stiffness and the damping ratio can be identified uniquely. The viscous damping coefficient and the material damping ratio can also be identified simultaneously in a numerical model structure. It is also shown that unfavorable effects by extraneous noises, including measurement noises, due to wind excitation, building facilities, and the motion of the occupants can be eliminated partially by using the present method. The accuracy of the present identification method is investigated through the actual records under limited observation in a base-isolated building.     

Impact of the Boeing 767 Aircraft into the World Trade Center

A numerical simulation of the aircraft impact into the exterior columns of the World Trade Center (WTC) was done using LS-DYNA. For simplification, the fuselage was modeled as a thin-walled cylinder, the wings were modeled as box beams with a fuel pocket, and the engines were represented as rigid cylinders. The exterior columns of the WTC were represented as box beams. Actual masses, material properties and dimensions of the Boeing 767 aircraft and the exterior columns of the WTC were used in this analysis. It was found that about 46% of the initial kinetic energy of the aircraft was used to damage columns. The minimum impact velocity of the aircraft to just penetrate the exterior columns would be 130?m/s. It was also found that a Boeing 767 traveling at top speed would not penetrate exterior columns of the WTC if the columns were thicker than 20?mm.     

Description of Structural Damage Caused by the Terrorist Attack on the Pentagon

On September 11, 2001, an airliner was intentionally crashed into the Pentagon. It struck at the first elevated slab on the west wall, and slid approximately 310?ft (94.5?m) diagonally into the building. The force of the collision demolished numerous columns and the fa?ade of the exterior wall, and induced damage to first-floor columns and the first elevated slab over an area approximately 90?ft (27.4?m) wide and 310?ft (94.5?m) long. None of the building collapsed immediately. The portion that remained standing, even after an intense fire, sustained substantial damage at the first-floor level.